feat(mobile-next): 补齐语音未听红点、录音浮层与 50-60s 时限

按 B-187 打回修复 4.3/4.4 阻塞项，输入框与按住说话改用 searchBg。

Co-authored-by: Cursor <cursoragent@cursor.com>
Co-authored-by: multica-agent <github@multica.ai>

mobile-next/lib/pages/chat/chat_view.dart

@@ -195,7 +195,9 @@ class ChatPage extends StatelessWidget {
               soundUrl: soundElem.sourceUrl,
               duration: soundElem.duration,
               isPlaying: logic.isPlaySound(message),
+              isUnread: !isISend && message.isRead == false,
             ),
+            false,
           );
         }
       }